Transfer case assembly having multiple gear mounting locations

ABSTRACT

A transfer case assembly includes an input gear, an idler gear, and an output gear. The idler gear is mounted on an idler shaft, which is rotatably supported by a bearing retained within a carrier. The carrier fits within an arcuate slot. The arcuate slot defines a multiple of idler shaft predetermined mounting locations. Each of the idler shaft predetermined mounting locations are equidistant from the third axis, and vary in distance from the first axis. For each of the idler shaft predetermined mounting locations a gear, of a predetermined size is provided to achieve a proper gear mesh for the desired gear ratio.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a gear assembly, and more particularly to a transfer case which provides multiple gear mounting locations to achieve multiple gear ratios within a common housing.

[0002] Transfer cases are known for transferring torque from an engine to front and rear vehicle wheels through a gear arrangement having an input shaft, an idler shaft, and an output shaft. Gears mounted upon each shaft mesh to form a specific gear ratio.

[0003] A common transfer case housing may be provided for multiple vehicle platforms.

[0004] However, each platform may require a different gear ratio. Within a transfer case housing openings for gear shafts are in fixed locations. If the size of one gear changes then all gears must be changed, as the shafts are in fixed locations. Thus, when a particular gear ratio is required, such as for a particular vehicle platform, all the gears are typically different designs to provide proper gear meshing. With a three gear system each new gear ratio will require three new parts using a conventional design approach. In some instances providing a particular gear ratio may require a different transfer case housing to accommodate the desired gear sizes.

[0005] Accordingly, it is desirable to provide a transfer case which minimizes the proliferation of parts while having the flexibility to contain different gear ratios within a common housing.

SUMMARY OF THE INVENTION

[0006] A transfer case assembly includes an input gear, an idler gear, and an output gear. The input gear is rotatably supported by an input shaft which rotates about a first axis. The input gear meshes with idler gear causing the idler gear to rotate. The idler gear is supported by an idler shaft which rotates about a second axis, parallel and offset from the first axis. The idler gear meshes with the output gear. The output gear is mounted on an output shaft which rotates about a third axis, parallel and offset from the second axis.

[0007] The idler shaft is rotatably supported by a bearing retained within a carrier which is moveable within an arcuate slot. The arcuate slot is inset within a wall of the transfer case housing. Within the arcuate slot there are a multiple of idler shaft predetermined mounting locations for the carrier.

[0008] Each of the idler shaft predetermined mounting locations corresponds to a predefined location for the second axis. The idler shaft predetermined mounting locations are equidistant from the third axis, and vary in distance from the first axis. For each of the idler shaft predetermined mounting locations an input gear of a particular predetermined size is required. Each predetermined mounting location thereby provides a different gear ratio.

[0009] The present invention therefore provides a transfer case having multiple gear mounting locations to achieve multiple desired gear ratios within a common housing while minimizing part proliferation.

BRIEF DESCRIPTON OF THE DRAWINGS

[0010] The present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0011]FIG. 1 is a sectional view of a transfer case assembly;

[0012]FIG. 2 is an enlarged perspective view of the idler shaft mounting arrangement;

[0013]FIG. 3 is an expanded sectional view of idler shaft mounting arrangement taken along the line 3-3 of FIG. 2;

[0014]FIG. 4a is a schematic view of a gear arrangement of the present invention in a first position;

[0015]FIG. 4b is a schematic view of a gear arrangement of the present invention in a second position; and

[0016]FIG. 5 is a schematic view of another transfer case assembly according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0017] A transfer case assembly 10 is shown in FIG. 1. It should be understood that other gear systems will benefit from the present invention. The transfer case assembly 10 includes an input gear 12, an idler gear 14, and an output gear 16. An input shaft 18 supports the input gear 12. The input shaft 18 rotates about a first axis 20. Rotation of the input shaft 18 causes the input gear 12 to rotate therewith. The input gear 12 meshes with idler gear 14 causing the idler gear 14 to rotate. An idler shaft 22 supports the idler gear 14. The idler shaft 22 rotates about a second axis 24. The second axis 24 is parallel and offset from the first axis 20. The idler gear 12 meshes with the output gear 16. The output gear 16 is mounted on an output shaft 26, which rotates about a third axis 28, parallel and offset from the second axis 24. The output shaft 26 carries the torque out of the transfer case assembly 10.

[0018] Referring to FIG. 2 a bearing 30 rotatably supports the idler shaft 22. The bearing 30 is retained within a carrier 32. The carrier 32 is fixably received within an arcuate slot 34 which is inset within an inner wall 35 (FIG. 3) of a transfer case housing 36. The rear wall 37 of the arcuate slot 34 is preferably offset from the inner wall 35 of the transfer case housing 36 such that the carrier 32 is essentially flush with the inner wall 35 when mounted.

[0019] The arcuate slot 34 defines a multiple of idler shaft predetermined mounting locations 38. The carrier 32 is mountable at each of the idler shaft predetermined mounting locations. A fastener 40, such as a pin, extends through an opening 42 in the carrier 32 and an opening 44 in the wall 35 of the transfer case housing 36 to retain the carrier 32. It should be understood that other fasteners such as bolts, welding, and the like will also benefit from the present invention.

[0020] Each of the idler shaft predetermined mounting locations 38 corresponds to a new location for the second axis 24. Openings 44 may be spaced such that they occur at a predefined distance from each other, or may be spaced according to specific predefined gear sizes. Openings 44 preferably correspond to the predetermined mounting location 38. The gear sizes are determined by the desired gear ratios to correspond with the predetermined mounting locations 38.

[0021] The arcuate slot 34 is preferably centered about the third axis 28. Each of the idler shaft predetermined mounting locations 38 is equidistant from the third axis 28, but vary in distance from the first axis 20. That is, at each predetermined mounting location, the third axis 28 is equidistant from the second axis 24, but the distance between the second axis 24 and the first axis 20 will vary based on the position of the arcuate slot 38.

[0022] The size of each input gear 12 corresponds to the varying distance from the second axis 24 to the first axis 20. For each of the idler shaft predetermined mounting locations 38 an input gear 12 of a particular predetermined size is required to achieve a proper gear mesh. Each particular input gear 12 provides as different gear ratio in combination with the other gears.

[0023] Referring to FIG. 4a, the second axis 24 has been fixed at one of the idler shaft predetermined mounting locations 38 a. The idler shaft predetermined mounting location 38 a corresponds to the size of the input gear 12 a to provide a desired gear ratio. FIG. 4b shows the second axis 24 fixed at another of the idler shaft predetermined mounting locations 38 b. The input gear 12 b shown corresponds to the second idler shaft predetermined mounting location 38 b to provide a second gear ratio. The output gear 16 and the idler gear 14 have not changed. The gear configuration shown in FIG. 4a provides a different gear ratio from the gear configuration shown in FIG. 4b with the change of only a single gear.

[0024] Referring to FIG. 5, the arcuate slot 34 is centered about the first axis 46. The output shaft 26 defines a third axis 48, parallel and offset from the first axis 46. In FIG. 5, each of the idler shaft predetermined mounting location 38′ are equidistant to the to first axis 46 and vary in distance relative to a third axis 28. That is, the arcuate slot 34′ defines a focus at the input shaft 18 as opposed to the output shaft 26. Each of the idler shaft predetermined mounting locations 38′ preferably corresponds with an output gear 16 of a particular predetermined size. Each output gear 16 corresponds to the varying distance between the third axis 28 and the second axis 24. Each particular output gear 16 provides a particular new gear ratio.

[0025] The invention has been described in an illustrative manner, and it is to be understood that the terminology that has been used is intended to be in the nature of words of description rather than of limitation. Obviously, modification and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claim the invention may be practiced otherwise than as specifically described. 

What is claimed is:
 1. A transfer case assembly for a vehicle comprising: a housing defining a multiple of idler shaft predetermined mounting locations; a first gear mounted on a first shaft, said first gear mounted within said housing and rotatable about a first axis; a second gear mounted on a second shaft, said second gear mounted within said housing and rotatable about a second axis, said second axis spaced from said first axis; and an idler gear mounted on an idler shaft, said idler shaft gear about a third axis such that said idler gear engages said first gear and said second gear, said idler shaft mounted at one of said multiple of idler shaft predetermined mounting locations.
 2. The transfer case assembly as recited in claim 1, further comprising a carrier to support said idler shaft.
 3. The transfer case assembly as recited in claim 2, wherein a wall of said housing defines an arcuate slot to receive said carrier.
 4. The transfer case assembly as recited in claim 3, wherein said arcuate slot defines said multiple of idler shaft predetermined mounting locations.
 5. The transfer case assembly as recited in claim 1, further comprising a pin to mount a carrier at any of said multiple of idler shaft predetermined mounting locations, said carrier operable to support said idler shaft.
 6. The transfer case assembly as recited in claim 5, wherein said pin is perpendicular to said carrier.
 7. The transfer case assembly as recited in claim 1, wherein said first gear is an input gear.
 8. The transfer case assembly as recited in claim 1, wherein said first gear is an output gear.
 9. The transfer case assembly as recited in claim 1, wherein the first gear is of a predetermined size, said predetermined size associated with one of said multiple of idler shaft predetermined mounting locations.
 10. The transfer case assembly as recited in claim 1, wherein each of said multiple of idler shaft predetermined mounting locations is equidistant from said first axis.
 11. A method of assembling a transfer case comprising of the steps of;
 1. mounting a first gear of a first size on a first shaft;
 2. locating the first shaft at a first predetermined mounting location, the first shaft defining a first axis of rotation;
 3. mounting a second gear of a second size on a second shaft;
 4. locating the second shaft at a second predetermined mounting location, the second shaft defining a second axis of rotation;
 5. mounting an idler gear to an idler shaft; and
 6. mounting the idler shaft at one of a plurality of predetermined idler shaft mounting locations in response to said step b) such that the idler gear engages the first gear and the second gear.
 12. The method according to claim 11, wherein said step a) further comprises selecting the first gear from a plurality of gears, each of the plurality of gears having a predetermined size associated with one of the plurality of predetermined idler shaft mounting locations.
 13. The method according to claim 12, wherein said step a) further comprises selecting the first gear size relative to the distance between the first axis and the one of the plurality of predetermined idler shaft mounting locations.
 14. The method according to claim 12 wherein said step a) further comprises selecting the first gear from a plurality of input gears, each of the plurality of input gears having a predetermined size.
 15. The method according to claim 12 wherein said step a) further comprises selecting the first gear from a plurality of output gears, each of the plurality of output gears having a predetermined size.
 16. The method according to claim 11, further comprises: g) mounting the idler shaft to a carrier prior to said step f).
 17. The method according to claim 11, wherein said step f) further comprises pinning the carrier within an arcuate slot at one of the plurality of predetermined idler shaft mounting locations. 